1. Field of the Invention
The present invention relates to an image-forming apparatus.
2. Related Background Art
There are conventionally an image-forming apparatus using an electron-emitting device, a plasma display panel (hereinafter briefly called a PDP), etc. as an image-forming apparatus of a flat type. Two kinds of electron-emitting devices using a thermionic cathode and a cold cathode are known as the electron-emitting device. For example, the above image-forming apparatus is disclosed in Japanese Patent Application Laid-open Nos. 62-200636, 62-252050, 05-74380, 04-43538, 08-264112, 08-321254 and 11-25860, and U.S. Pat. No. 3,896,324, etc.
A field emission type (FE type), a metal/insulating layer/metal (MIM type), a surface conduction type, etc. begin to be practically used in the cold cathode.
In the image-forming apparatus using the electron-emitting device, the electron-emitting device and an image forming member are arranged within an airtight container. More concretely, electrons emitted from plural electron-emitting devices arranged on a rear plate are irradiated to a fluorescent substance (image forming member) on a face plate arranged oppositely to the rear plate so that an image is formed.
For example, when the above image-forming apparatus is used as a display, it is necessary to apply a high voltage of from several kV to several tens kV to the image forming member (fluorescent substance). Therefore, the above rear plate and the face plate are spaced from each other by a supporting member called an outer frame, etc. at a predetermined distance to secure a sufficient electric insulating property between the face plate and the rear plate. Joining portions of the above supporting member and the rear and face plates (outer circumferential portions of both the plates) are joined (airtightly sealed) to each other by a joining member so that the airtight container is formed. A pressure reducing state required to emit electrons is formed within the airtight container.
Here, one example of the structure and a manufacturing method of a conventional airtight container will be briefly explained on the basis of FIG. 7.
As shown in FIG. 7, an airtight container 710 is constructed by a rear plate 702, a face plate 701 and a supporting member 703. The supporting member 703 is formed by four structural members 703-1, 703-2, 703-3 and 703-4 formed in a plate shape (a rectangular parallelepiped).
The supporting member 703 is prepared by combining the above four structural members with each other in a frame shape and fixing these members to each other in advance by a bond such as low melting point glass.
A joining layer 704 such as low melting point glass is next formed in a joining portion of the rear plate 702 and the face plate 701. Thereafter, the supporting member 703 is nipped at a center and the rear plate 702 and the face plate 701 are aligned and stuck to each other. Further, while a load is applied to the rear and face plates, these plates are heated to a softening temperature of the joining layer 704 and are then cooled. Finally, the interior of the container is evacuated through an exhaust pipe (not shown) and a vacuum atmosphere or a gas atmosphere is formed within the container. Thereafter, the container is sealed by using a sealing method of the exhaust pipe, or an exhaust-pipeless method for forming the above atmosphere within a vacuum chamber and performing a seal attaching operation so that the airtight container 710 is completed.